ObjectivePeople with early-onset colorectal cancer (EOCRC), defined as colorectal cancer (CRC) before the age of 50, now constitute a significant patient population. In empirical and grey literature EOCRC patients report unsatisfactory experiences of care, especially in relation to protracted intervals from first help-seeking to diagnosis. This study is the first to investigate EOCRC patients’ perspectives on ways to improve experiences of care. The objective is to provide foundational knowledge for the development of EOCRC-specific patient-reported experience measures (PREMs).DesignThe study was designed as qualitative Internet Mediated Research, involving a thematic analysis of unsolicited narratives recounting personal experiences of EOCRC care. We examined advice-giving statements in 120 online texts written by EOCRC patients and survivors.SettingThe Internet is the broad research setting. The host websites of three prominent charitable CRC support organisations were selected as specific research sites: Bowel Cancer Australia, Bowel Cancer UK and Bowel Cancer New Zealand.ResultsWe found that 90% of texts comprised statements of advice to new patients about the importance of self-advocacy in achieving quality care. Four key contexts for self-advocacy were identified: (1) accessing relevant diagnostic services; (2) driving diagnostic investigations when symptoms are not resolved; (3) involvement in treatment decision-making and (4) proactivity about preferred outcomes. Over 30% of advice-giving texts also directed statements of advice to healthcare providers, indicating that their youthfulness had been a barrier to timely diagnosis.ConclusionHealthcare barriers to, and facilitators of, patient self-advocacy may be indicators of quality EORC care. There is a need for greater awareness of the impact of age bias on the responsiveness of clinicians and healthcare services in EOCRC care. Our findings support the development of EOCRC-specific PREMs that can guide age-appropriate policy and practice for this newly identified patient population.